Ambient temperature of battery bank

Brewgonia
Brewgonia Solar Expert Posts: 31 ✭
in Solar Beginners Corner #1
Living outside of Chicago means cold winters and moderate summers. What is the optimum temperature range of the battery bank box/room? I have the option of building a vented box inside a heated pole barn or, insulating a small shed next to the pole barn. I can always install a small DC heater for the shed during the winter.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Ambient temperature of battery bank
    Brewgonia wrote: »
    Living outside of Chicago means cold winters and moderate summers. What is the optimum temperature range of the battery bank box/room? I have the option of building a vented box inside a heated pole barn or, insulating a small shed next to the pole barn. I can always install a small DC heater for the shed during the winter.

    Batteries are rated at "room temperature"; around 20-25 degrees Celsius (68-77 degrees Fahrenheit).

    Hotter temps are worse on them as it accelerates the chemical activity. Colder temps cause a loss of capacity but don't harm the batteries. Charged batteries do not freeze at normal cold temperatures.
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  • Brewgonia
    Brewgonia Solar Expert Posts: 31 ✭
    #3
    Re: Ambient temperature of battery bank
    Cariboocoot wrote: »
    Batteries are rated at "room temperature"; around 20-25 degrees Celsius (68-77 degrees Fahrenheit).

    Hotter temps are worse on them as it accelerates the chemical activity. Colder temps cause a loss of capacity but don't harm the batteries. Charged batteries do not freeze at normal cold temperatures.
    Thanks Cariboocoot! If I go the shed route it sounds like I'll have to be more concerned with it getting too hot rather than cold if properly charged.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Ambient temperature of battery bank

    My battery bank, the original which lasted 11 years, and now the new ones, are out in an unheated shed. The batteries themselves were down as low as minus 7C this winter after an extended period of minus 20C weather. At that minus 7C temp, the controllers had the absorb voltage hanging around 15.5, the highest my inverters could handle before shutting down. Added insulation around the bank, like I used to do years ago, and the battery temp over a day or so, came up to 0C and hasn't gone lower than minus 1 or 2C since. They generate some internal heat when charging and discharging. Come warmer weather of course I remove the insulation so they don't overheat.
    I've always suspected these colder temps contributed to the first bank lasting 11 years.
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  • Brewgonia
    Brewgonia Solar Expert Posts: 31 ✭
    #5
    Re: Ambient temperature of battery bank

    This winter has been pretty bad for us (probably nothing to you!) with sustained temps below 0*f for weeks. After reading your experience I am definitely leaning toward housing my batteries in the shed, adding removeable insulation.

    For the summer months I plan on having a small DC computer fan or two installed in the battery box to assist with circulation and expel any hydrogen gas.
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  • SolInvictus
    SolInvictus Solar Expert Posts: 138 ✭
    #6
    Re: Ambient temperature of battery bank

    The fan could potentially ignite the hydrogen. Put air vents at the top of the walls of the battery box and insulate the sides and bottoms of the batteries. You could paint the battery box white on the outside or use aluminum sheeting to reflect sunlight in the summer to help keep the batteries cool.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Ambient temperature of battery bank
    SolInvictus wrote: »
    The fan could potentially ignite the hydrogen.

    And yet many, many people use such fans to provide positive ventilation of their battery boxes and none of them blow up. The risk is so miniscule for this as to be non-existent. The wires connected to the batteries could also spark and cause them to explode. That doesn't actually happen either. Aliens could point their death beams at them from outer space ....

    There is such a thing as being paranoid, you know.
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  • Brewgonia
    Brewgonia Solar Expert Posts: 31 ✭
    #8
    Re: Ambient temperature of battery bank
    Cariboocoot wrote: »
    And yet many, many people use such fans to provide positive ventilation of their battery boxes and none of them blow up. The risk is so miniscule for this as to be non-existent. The wires connected to the batteries could also spark and cause them to explode. That doesn't actually happen either. Aliens could point their death beams at them from outer space ....

    There is such a thing as being paranoid, you know.

    You make a BIG funny!

    Thanks for everyone's views, much appreciated.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #9
    Re: Ambient temperature of battery bank
    Cariboocoot wrote: »
    And yet many, many people use such fans to provide positive ventilation of their battery boxes and none of them blow up. The risk is so miniscule for this as to be non-existent.

    I agree, as long as the fan turns on whenever there is charging. I think there is somewhat greater risk if you use a voltage controlled switch (or aux output), because a shorted cell could cause hydrogen production at a charging voltage that is below normal gassing voltage.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • 8n-bob
    8n-bob Solar Expert Posts: 35 ✭✭
    #10
    Re: Ambient temperature of battery bank

    Jumping in on this thread with a question

    So if your solar cells are in the 30 volt range could you just wire the fan with a resistor to the solar cell side and when ever there is voltage the fan would be turning. Since the fan is 12vdc the resistor would limit current and keep the fan from running away. Or is my thinking way off.

    I am getting ready to build a battery box for 4 sets (8 golf cart batt's) for a 12 V system and was thinking of hooking up the fan that way. Or should the fan just be on the 12v side and run 24/7.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #11
    Re: Ambient temperature of battery bank
    8n-bob wrote: »
    Jumping in on this thread with a question

    So if your solar cells are in the 30 volt range could you just wire the fan with a resistor to the solar cell side and when ever there is voltage the fan would be turning. Since the fan is 12vdc the resistor would limit current and keep the fan from running away. Or is my thinking way off.

    I am getting ready to build a battery box for 4 sets (8 golf cart batt's) for a 12 V system and was thinking of hooking up the fan that way. Or should the fan just be on the 12v side and run 24/7.

    You could do this with a solar panel dedicated to running the fan. DC fan motors are pretty easy going about Voltage and it would run up to speed as the insolation on the panel increased. You probably would not need a limiting resistor as many of them can take >12 VDC anyway (check the unit, as always).

    You don't want to tap off your charging array for this because the resistance of the fan on the panels could skew the charge controller (again depending on exactly what equipment we're dealing with).
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,601 admin
    #12
    Re: Ambient temperature of battery bank

    Also, 24 volt DC computer fans are pretty common. Used they are frequently less because most people are looking for 12 volt fans for their projects.

    Connect a 24 volt fan to your array--Check its operation and if it is running too fast--Then look at adding a power resistor to drop a few volts.

    Note, the Vmp~30 volts may become close to 40 volts Voc (charge controller says batteries are full and cuts back on charging current). So see how the fan behaves--You may still need the resistor (or a few diodes in series) to keep the voltage reasonable.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #13
    Re: Ambient temperature of battery bank

    And many (but not all) 24 volt computer fans will operate fine on 12 volts, just at a reduced speed and of course airflow. But depending on your set up, you may not need wind blasting through at full speed. Just a thought.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #14
    Re: Ambient temperature of battery bank

    My battery box has a slanted cover with plenty of opening at the high point. This allows any hydrogen, which is far lighter than air, to naturally seek the high end of the lid where the venting is, and escape without any problems. There's also a vent at the bottom to admit fresh flow through air. Works awesome for me. Of course if my battery box was inside living space, I'd probably vent outside.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #15
    Re: Ambient temperature of battery bank
    8n-bob wrote: »
    Jumping in on this thread with a question
    <snip>
    I am getting ready to build a battery box for 4 sets (8 golf cart batt's) for a 12 V system

    Four parallel batteries is NOT good design. short discussion here. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #16
    Re: Ambient temperature of battery bank
    vtmaps wrote: »
    Four parallel batteries is NOT good design.

    TOTALLY agree. My previous battery bank consisted of just 3 parallel strings, and required great care in how they were wired together and constant monitoring to prevent drift between batteries.
    That's why, when they needed to be replaced, I went with a single string of 2 volt cells. And in in addition, I now have only 6 battery caps to remove and 6 cells to water - - - instead of the 18 I used to have. So much better in so many ways.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: Ambient temperature of battery bank
    vtmaps wrote: »
    Four parallel batteries is NOT good design. short discussion here. --vtMaps

    Ditto.
    If you need that much stored power you should probably go to 24 Volts (if at all possible).
    A bit about system Voltages: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
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  • rgearhead
    rgearhead Solar Expert Posts: 38 ✭
    #18
    Re: Ambient temperature of battery bank

    I found this thread at the right time, as I'm in the same boat as the OP with battery's that have been sitting..in my cool basement garage...but im not dealing with near as many battery's... I have just 6 6 volt deep cycle battery's wired series - parallel making a 12 volt bank. and i was going to give them a charge today as they just been sitting.. the voltage right now is 12.37v I have a pretty big car charger that can do 2 amp, 10 amp , 40 amp and 200 amp..was thinking of hitting them with 40 amp for an hour but figured i better ask people in the know..
    the battery's are 230amp hour battery's..
    more specks
    20 amp hour rate:230
    5 amp hour rate:174
    6 amp hour rate:178
    BCI Group Size:GC2
    Minutes at 25 amps:448
    Minutes at 75 amps:120
    Volts:6

    thanks for any thoughts or in put.. im a noob..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #19
    Re: Ambient temperature of battery bank
    rgearhead wrote: »
    I found this thread at the right time, as I'm in the same boat as the OP with battery's that have been sitting..in my cool basement garage...but im not dealing with near as many battery's... I have just 6 6 volt deep cycle battery's wired series - parallel making a 12 volt bank. and i was going to give them a charge today as they just been sitting.. the voltage right now is 12.37v I have a pretty big car charger that can do 2 amp, 10 amp , 40 amp and 200 amp..was thinking of hitting them with 40 amp for an hour but figured i better ask people in the know..
    the battery's are 230amp hour battery's..
    more specks
    20 amp hour rate:230
    5 amp hour rate:174
    6 amp hour rate:178
    BCI Group Size:GC2
    Minutes at 25 amps:448
    Minutes at 75 amps:120
    Volts:6

    thanks for any thoughts or in put.. im a noob..

    Okay so six 6 Volts configured for 12 Volt means three parallel strings. Right there you're asking for imbalance trouble.
    It also means 3 * 230 Amp hours: 690 total. As one bank that will have no problem accepting 40 Amps of charge current.
    What they aren't going to get from the automotive charger is proper Absorb Voltage and time, because that type of charger isn't designed to do that.
    But it will be better than letting them self-discharge for months on end.

    As a rule batteries are the last thing you want to get for the system. That way they are new manufacture (check) and haven't already been aging while everything else gets put together.
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  • rgearhead
    rgearhead Solar Expert Posts: 38 ✭
    #20
    Re: Ambient temperature of battery bank

    thanks Cariboocoot.. figuring i might have several things gonna be off balance seeing as im slowly piecing this little set up together..mainly building it for emergency back for when the power goes out..

    so 3 parallel sets is a bad thing, 4 would have been the way to go ? I also i have collected some other prices such as 2 -195 watt grape solar panels at 5.38 amp's and 36.2 volts each and one 250 watt grape solar panel at 8.15 amp's and 30.7 volts ..
    the 2 -195 are to go in 1 area and the 250 watt another and i have bought one tristar 45 MPPT charger thus far and collected enough right size cable. but now need to figgure out how to hobble it together n make it work, at least get it up n running..

    what can 640 watts worth of panels Handel battery bank wise, even better whats the formal ..

    thanks..
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #21
    Re: Ambient temperature of battery bank
    rgearhead wrote: »
    thanks Cariboocoot.. figuring i might have several things gonna be off balance seeing as im slowly piecing this little set up together..mainly building it for emergency back for when the power goes out..

    so 3 parallel sets is a bad thing, 4 would have been the way to go ? I also i have collected some other prices such as 2 -195 watt grape solar panels at 5.38 amp's and 36.2 volts each and one 250 watt grape solar panel at 8.15 amp's and 30.7 volts ..
    the 2 -195 are to go in 1 area and the 250 watt another and i have bought one tristar 45 MPPT charger thus far and collected enough right size cable. but now need to figgure out how to hobble it together n make it work, at least get it up n running..

    what can 640 watts worth of panels Handel battery bank wise, even better whats the formal ..

    thanks..

    No, two parallel battery strings would have been the way to go: the more in parallel the greater the potential for problems.

    Your panels don't match Vmp by more than 10%. In other words the 36 Vmp panels and the 20 Vmp panel aren't going to play nice together: the higher Voltage will 'pull' the lower one up above Vmp, thereby reducing its current output. You really don't want panels in different locations on the same controller either. Oh some say it will work, but how well will it work? They certainly won't combine to give you full power because they won't have the same amount of light on them at the same time.

    If they were all compatible and in the same location 640 Watts of panel could put out 42 Amps on a 12 Volt system - enough for 420 Amp hours. Of course half that @ 24 Volts and half again at 48.
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #22
    Re: Ambient temperature of battery bank
    rgearhead wrote: »
    I have just 6 6 volt deep cycle battery's wired series - parallel making a 12 volt bank. and i was going to give them a charge today as they just been sitting.. the voltage right now is 12.37v I have a pretty big car charger that can do 2 amp, 10 amp , 40 amp and 200 amp..was thinking of hitting them with 40 amp for an hour but figured i better ask people in the know..

    As Cariboocoot mentioned, a car charger is probably not going to properly charge those batteries.

    The problem with three parallel batteries is that the current doesn't divide equally among the three batteries while they are charging. This can actually be dangerous if your entire amperage is all going through just one battery.

    Many folks running parallel batteries get a DC current clamp meter to check for battery balance while charging. The best thing you can do is charge your parallel batteries one string at a time. And get an hydrometer to check the specific gravity of the batteries.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • rgearhead
    rgearhead Solar Expert Posts: 38 ✭
    #23
    Re: Ambient temperature of battery bank
    vtmaps wrote: »
    As Cariboocoot mentioned, a car charger is probably not going to properly charge those batteries.

    The problem with three parallel batteries is that the current doesn't divide equally among the three batteries while they are charging. This can actually be dangerous if your entire amperage is all going through just one battery.

    Many folks running parallel batteries get a DC current clamp meter to check for battery balance while charging. The best thing you can do is charge your parallel batteries one string at a time. And get an hydrometer to check the specific gravity of the batteries.

    --vtMaps
    thanks cariboocoot and vtmaps... so if i was running 8 battery's in a parallel - series = 4, it safer than 3 ?

    here to learn, thanks...
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #24
    Re: Ambient temperature of battery bank
    rgearhead wrote: »
    thanks cariboocoot and vtmaps... so if i was running 8 battery's in a parallel - series = 4, it safer than 3 ?

    here to learn, thanks...

    One battery string is great.
    Two parallel strings is good.
    Three is getting 'dicey'.
    Four you'd better watch it carefully.
    Five ... you must like to spend money on batteries.

    In all cases you want the wiring right. With two parallel strings you can connect the positive and negative wires to the system 'diagonally'; one on one string, the other on the other. This is to keep the wire lengths (and thus resistance) even between both. With three or more it's best to go with common connection points/bus bars for them.

    Some basic stuff on wiring batteries in parallel: http://www.smartgauge.co.uk/batt_con.html
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  • 8n-bob
    8n-bob Solar Expert Posts: 35 ✭✭
    #25
    Re: Ambient temperature of battery bank

    I did not think of that Cariboocoot. I have several small 12v solar cells that I could put up that would be for service power. Could even put a little gel-cell in the system and the fan would run till the batt went dead. A little extra ventilation after the sun went down. Then the next time the sun was up it would run the fan and charge the gel-cell.

    Kinda like Service Power in a hydro plant. A small generator for in house power use. :-)

    Some times you don't see the forest through the trees.

    Thanks
    BobO.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #26
    Re: Ambient temperature of battery bank
    8n-bob wrote: »
    I did not think of that Cariboocoot. I have several small 12v solar cells that I could put up that would be for service power. Could even put a little gel-cell in the system and the fan would run till the batt went dead. A little extra ventilation after the sun went down. Then the next time the sun was up it would run the fan and charge the gel-cell.

    Kinda like Service Power in a hydro plant. A small generator for in house power use. :-)

    Some times you don't see the forest through the trees.

    Thanks
    BobO.

    Problem with putting the gel cell in the circuit and letting it run until it's dead: it's dead. Batteries do not take kindly to being totally discharged.

    When you put a battery in you want to use a controller with an LVD for loads so that it is not over-charged nor drawn dead. Example: http://www.solar-electric.com/ss-6l.html
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  • 8n-bob
    8n-bob Solar Expert Posts: 35 ✭✭
    #27
    Re: Ambient temperature of battery bank

    True: I should have thought about that. But in any case I tend to do things overly complex. I'll prob just do the solar cell and fan when I reach that point. :-)

    Have a great day
    BobO.
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